1. Field of the Invention
This invention relates to optometers and particularly to a Scheiner-principle optometer apparatus, and method therefore, for measuring the resting state of accommodation, and for providing recognition of this accommodative state in a machine readable format to ancillary devices, such as to a computer.
2. Description of the Prior Art
This application is an improvement on the related invention of U.S. Pat. No. 4,997,269 entitled "SCHEINER-PRINCIPLE POCKET OPTOMETER FOR SELF EVALUATION AND BIOFEEDBACK ACCOMMODATION TRAINING" both of which have the same inventor and are commonly assigned to the Government of the United States. The need for precise lens accommodation to bring visual targets into sharp focus on the retina is far more urgent at night when contrast is very low, than in bright daylight. Unfortunately, it is at precisely this time that many individuals become myopic and further reduce the quality of an already poor visual image. In many professions this phenomenon, sometimes called the "dark focus of accommodation", is of little consequence. For pilots flying at night, however, it can mean the difference between life and death. A reliable screening instrument capable of measuring the refractive state of individuals in the dark could, therefore, provide useful preventive information. In those situations where feedback to the individual being tested is undesirable, such as when screening potential pilot candidates or making wardroom assessments before night operations, some means must be provided to enable a second party to "read" the optometer. The optometer disclosed herein provides a means to convert the optometer setting into machine readable formats such as a voltage level, or binary coded decimal or straight binary encoding, which could then be input directly to a small computer or remote display device for evaluation.